I know that if you have the completed zeta relic you become able to purchase its replicas, provided it is somewhere on your person (and not on a retainer)

What I'm wondering about is what happens if you convert the zeta into the astral/umbral nodes for the 3.x relic. Does the game just remember that you've done that, and that you become able to buy replicas for that weapon without needing that weapon in your inventory anymore (since you'd obviously no longer have it anymore)? I'm assuming this is how it works but wanted to get 100% confirmation from someone who's done it.

I originally wanted to keep my zeta relics for "posterity" but there have been several instances now where I went to Hyrstmill to fetch a replica, only to have to go to Hyrstmill *twice* because I forgot to bring the zeta with me. If this is a hassle I could get rid of by converting the zeta relics into nodes, I may very well do it...